wip buffer_type helper but without auto downcasting, doesnt work due to AnyBuffer limitations

Signed-off-by: Teo Koon Peng <teokoonpeng@gmail.com>

Author: koonpeng

macros/src/buffer.rs

@@ -1,24 +1,29 @@
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
-use syn::{parse_quote, Ident, ItemStruct, Type};
+use syn::{parse_quote, Field, Generics, Ident, ItemStruct, Type, TypePath};
 
 use crate::Result;
 
 pub(crate) fn impl_joined_value(input_struct: &ItemStruct) -> Result<TokenStream> {
     let struct_ident = &input_struct.ident;
     let (impl_generics, ty_generics, where_clause) = input_struct.generics.split_for_impl();
-    let (field_ident, field_type) = get_fields_map(&input_struct.fields)?;
-    let BufferStructConfig {
-        struct_name: buffer_struct_ident,
-    } = BufferStructConfig::from_data_struct(&input_struct);
+    let StructConfig {
+        buffer_struct_name: buffer_struct_ident,
+    } = StructConfig::from_data_struct(&input_struct);
     let buffer_struct_vis = &input_struct.vis;
 
+    let (field_ident, _, field_config) = get_fields_map(&input_struct.fields)?;
+    let buffer_type: Vec<&Type> = field_config
+        .iter()
+        .map(|config| &config.buffer_type)
+        .collect();
+
     let buffer_struct: ItemStruct = parse_quote! {
         #[derive(Clone)]
         #[allow(non_camel_case_types)]
         #buffer_struct_vis struct #buffer_struct_ident #impl_generics #where_clause {
             #(
-                #buffer_struct_vis #field_ident: ::bevy_impulse::Buffer<#field_type>,
+                #buffer_struct_vis #field_ident: #buffer_type,
             )*
         }
     };
@@ -36,7 +41,7 @@ pub(crate) fn impl_joined_value(input_struct: &ItemStruct) -> Result<TokenStream
         impl #impl_generics #struct_ident #ty_generics #where_clause {
             fn select_buffers(
                 #(
-                    #field_ident: ::bevy_impulse::Buffer<#field_type>,
+                    #field_ident: #buffer_type,
                 )*
             ) -> #buffer_struct_ident #ty_generics {
                 #buffer_struct_ident {
@@ -55,14 +60,30 @@ pub(crate) fn impl_joined_value(input_struct: &ItemStruct) -> Result<TokenStream
     Ok(gen.into())
 }
 
-struct BufferStructConfig {
-    struct_name: Ident,
+/// Converts a list of generics to a [`PhantomData`] TypePath.
+/// e.g. `::std::marker::PhantomData<(T,)>`
+// Currently unused but could be used in the future
+fn _to_phantom_data(generics: &Generics) -> TypePath {
+    let lifetimes: Vec<Type> = generics
+        .lifetimes()
+        .map(|lt| {
+            let lt = &lt.lifetime;
+            let ty: Type = parse_quote! { & #lt () };
+            ty
+        })
+        .collect();
+    let ty_params: Vec<&Ident> = generics.type_params().map(|ty| &ty.ident).collect();
+    parse_quote! { ::std::marker::PhantomData<(#(#lifetimes,)* #(#ty_params,)*)> }
+}
+
+struct StructConfig {
+    buffer_struct_name: Ident,
 }
 
-impl BufferStructConfig {
+impl StructConfig {
     fn from_data_struct(data_struct: &ItemStruct) -> Self {
         let mut config = Self {
-            struct_name: format_ident!("__bevy_impulse_{}_Buffers", data_struct.ident),
+            buffer_struct_name: format_ident!("__bevy_impulse_{}_Buffers", data_struct.ident),
         };
 
         let attr = data_struct
@@ -72,8 +93,39 @@ impl BufferStructConfig {
 
         if let Some(attr) = attr {
             attr.parse_nested_meta(|meta| {
-                if meta.path.is_ident("struct_name") {
-                    config.struct_name = meta.value()?.parse()?;
+                if meta.path.is_ident("buffer_struct_name") {
+                    config.buffer_struct_name = meta.value()?.parse()?;
+                }
+                Ok(())
+            })
+            // panic if attribute is malformed, this will result in a compile error which is intended.
+            .unwrap();
+        }
+
+        config
+    }
+}
+
+struct FieldConfig {
+    buffer_type: Type,
+}
+
+impl FieldConfig {
+    fn from_field(field: &Field) -> Self {
+        let ty = &field.ty;
+        let mut config = Self {
+            buffer_type: parse_quote! { ::bevy_impulse::Buffer<#ty> },
+        };
+
+        let attr = field
+            .attrs
+            .iter()
+            .find(|attr| attr.path().is_ident("buffers"));
+
+        if let Some(attr) = attr {
+            attr.parse_nested_meta(|meta| {
+                if meta.path.is_ident("buffer_type") {
+                    config.buffer_type = meta.value()?.parse()?;
                 }
                 Ok(())
             })
@@ -85,20 +137,22 @@ impl BufferStructConfig {
     }
 }
 
-fn get_fields_map(fields: &syn::Fields) -> Result<(Vec<&Ident>, Vec<&Type>)> {
+fn get_fields_map(fields: &syn::Fields) -> Result<(Vec<&Ident>, Vec<&Type>, Vec<FieldConfig>)> {
     match fields {
         syn::Fields::Named(data) => {
             let mut idents = Vec::new();
             let mut types = Vec::new();
+            let mut configs = Vec::new();
             for field in &data.named {
                 let ident = field
                     .ident
                     .as_ref()
                     .ok_or("expected named fields".to_string())?;
                 idents.push(ident);
                 types.push(&field.ty);
+                configs.push(FieldConfig::from_field(field));
             }
-            Ok((idents, types))
+            Ok((idents, types, configs))
         }
         _ => return Err("expected named fields".to_string()),
     }
@@ -113,7 +167,11 @@ fn impl_buffer_map_layout(
 ) -> Result<proc_macro2::TokenStream> {
     let struct_ident = &buffer_struct.ident;
     let (impl_generics, ty_generics, where_clause) = buffer_struct.generics.split_for_impl();
-    let (field_ident, field_type) = get_fields_map(&item_struct.fields)?;
+    let (field_ident, _, field_config) = get_fields_map(&item_struct.fields)?;
+    let buffer_type: Vec<&Type> = field_config
+        .iter()
+        .map(|config| &config.buffer_type)
+        .collect();
     let map_key: Vec<String> = field_ident.iter().map(|v| v.to_string()).collect();
 
     Ok(quote! {
@@ -128,16 +186,18 @@ fn impl_buffer_map_layout(
             fn try_from_buffer_map(buffers: &::bevy_impulse::BufferMap) -> Result<Self, ::bevy_impulse::IncompatibleLayout> {
                 let mut compatibility = ::bevy_impulse::IncompatibleLayout::default();
                 #(
-                    let #field_ident = if let Ok(buffer) = compatibility.require_message_type::<#field_type>(#map_key, buffers) {
+                    let #field_ident = if let Ok(buffer) = compatibility.require_buffer_type::<#buffer_type>(#map_key, buffers) {
                         buffer
                     } else {
                         return Err(compatibility);
                     };
                 )*
 
-                Ok(Self {#(
-                    #field_ident,
-                )*})
+                Ok(Self {
+                    #(
+                        #field_ident,
+                    )*
+                })
             }
         }
     }
@@ -154,7 +214,7 @@ fn impl_joined(
     let struct_ident = &joined_struct.ident;
     let item_struct_ident = &item_struct.ident;
     let (impl_generics, ty_generics, where_clause) = item_struct.generics.split_for_impl();
-    let (field_ident, _) = get_fields_map(&item_struct.fields)?;
+    let (field_ident, _, _) = get_fields_map(&item_struct.fields)?;
 
     Ok(quote! {
         impl #impl_generics ::bevy_impulse::Joined for #struct_ident #ty_generics #where_clause {

src/buffer/any_buffer.rs

@@ -121,6 +121,10 @@ impl AnyBuffer {
             .ok()
             .map(|x| *x)
     }
+
+    pub fn as_any_buffer(&self) -> Self {
+        self.clone().into()
+    }
 }
 
 impl<T: 'static + Send + Sync + Any> From<Buffer<T>> for AnyBuffer {

src/buffer/buffer_map.rs

@@ -315,12 +315,15 @@ impl Accessed for BufferMap {
 mod tests {
     use crate::{prelude::*, testing::*, BufferMap};
 
-    #[derive(Clone, JoinedValue)]
+    #[derive(JoinedValue)]
     struct TestJoinedValue<T: Send + Sync + 'static + Clone> {
         integer: i64,
         float: f64,
         string: String,
         generic: T,
+        #[buffers(buffer_type = AnyBuffer)]
+        #[allow(unused)]
+        any: AnyMessageBox,
     }
 
     #[test]
@@ -332,26 +335,32 @@ mod tests {
             let buffer_f64 = builder.create_buffer(BufferSettings::default());
             let buffer_string = builder.create_buffer(BufferSettings::default());
             let buffer_generic = builder.create_buffer(BufferSettings::default());
+            let buffer_any = builder.create_buffer(BufferSettings::default());
 
             let mut buffers = BufferMap::default();
             buffers.insert("integer", buffer_i64);
             buffers.insert("float", buffer_f64);
             buffers.insert("string", buffer_string);
             buffers.insert("generic", buffer_generic);
+            buffers.insert("any", buffer_any);
 
             scope.input.chain(builder).fork_unzip((
                 |chain: Chain<_>| chain.connect(buffer_i64.input_slot()),
                 |chain: Chain<_>| chain.connect(buffer_f64.input_slot()),
                 |chain: Chain<_>| chain.connect(buffer_string.input_slot()),
                 |chain: Chain<_>| chain.connect(buffer_generic.input_slot()),
+                |chain: Chain<_>| chain.connect(buffer_any.input_slot()),
             ));
 
             builder.try_join(&buffers).unwrap().connect(scope.terminate);
         });
 
         let mut promise = context.command(|commands| {
             commands
-                .request((5_i64, 3.14_f64, "hello".to_string(), "world"), workflow)
+                .request(
+                    (5_i64, 3.14_f64, "hello".to_string(), "world", ()),
+                    workflow,
+                )
                 .take_response()
         });
 
@@ -373,27 +382,33 @@ mod tests {
             let buffer_f64 = builder.create_buffer(BufferSettings::default());
             let buffer_string = builder.create_buffer(BufferSettings::default());
             let buffer_generic = builder.create_buffer(BufferSettings::default());
+            let buffer_any = builder.create_buffer::<()>(BufferSettings::default());
+
+            scope.input.chain(builder).fork_unzip((
+                |chain: Chain<_>| chain.connect(buffer_i64.input_slot()),
+                |chain: Chain<_>| chain.connect(buffer_f64.input_slot()),
+                |chain: Chain<_>| chain.connect(buffer_string.input_slot()),
+                |chain: Chain<_>| chain.connect(buffer_generic.input_slot()),
+                |chain: Chain<_>| chain.connect(buffer_any.input_slot()),
+            ));
 
             let buffers = TestJoinedValue::select_buffers(
                 buffer_i64,
                 buffer_f64,
                 buffer_string,
                 buffer_generic,
+                buffer_any.into(),
             );
 
-            scope.input.chain(builder).fork_unzip((
-                |chain: Chain<_>| chain.connect(buffers.integer.input_slot()),
-                |chain: Chain<_>| chain.connect(buffers.float.input_slot()),
-                |chain: Chain<_>| chain.connect(buffers.string.input_slot()),
-                |chain: Chain<_>| chain.connect(buffers.generic.input_slot()),
-            ));
-
             builder.join(buffers).connect(scope.terminate);
         });
 
         let mut promise = context.command(|commands| {
             commands
-                .request((5_i64, 3.14_f64, "hello".to_string(), "world"), workflow)
+                .request(
+                    (5_i64, 3.14_f64, "hello".to_string(), "world", ()),
+                    workflow,
+                )
                 .take_response()
         });
 
@@ -419,19 +434,25 @@ mod tests {
                 JsonBuffer::from(builder.create_buffer::<String>(BufferSettings::default()));
             let buffer_generic =
                 JsonBuffer::from(builder.create_buffer::<String>(BufferSettings::default()));
+            let buffer_any =
+                JsonBuffer::from(builder.create_buffer::<()>(BufferSettings::default()));
 
             let buffers = TestJoinedValue::select_buffers(
                 buffer_i64.downcast_for_message().unwrap(),
                 buffer_f64.downcast_for_message().unwrap(),
                 buffer_string.downcast_for_message().unwrap(),
                 buffer_generic.downcast_for_message().unwrap(),
+                buffer_any.downcast_buffer().unwrap(),
             );
 
             scope.input.chain(builder).fork_unzip((
                 |chain: Chain<_>| chain.connect(buffers.integer.input_slot()),
                 |chain: Chain<_>| chain.connect(buffers.float.input_slot()),
                 |chain: Chain<_>| chain.connect(buffers.string.input_slot()),
                 |chain: Chain<_>| chain.connect(buffers.generic.input_slot()),
+                |chain: Chain<_>| {
+                    chain.connect(buffers.any.downcast_for_message().unwrap().input_slot())
+                },
             ));
 
             builder.join(buffers).connect(scope.terminate);
@@ -440,7 +461,13 @@ mod tests {
         let mut promise = context.command(|commands| {
             commands
                 .request(
-                    (5_i64, 3.14_f64, "hello".to_string(), "world".to_string()),
+                    (
+                        5_i64,
+                        3.14_f64,
+                        "hello".to_string(),
+                        "world".to_string(),
+                        (),
+                    ),
                     workflow,
                 )
                 .take_response()
@@ -456,7 +483,7 @@ mod tests {
     }
 
     #[derive(Clone, JoinedValue)]
-    #[buffers(struct_name = FooBuffers)]
+    #[buffers(buffer_struct_name = FooBuffers)]
     struct TestDeriveWithConfig {}
 
     #[test]